This invention relates to equipment for divers and in particular for scuba divers.
Divers have one eternal worry namely accumulating too much nitrogen in their blood. The United States Navy has developed tables which guide a diver as to when and how long he can safely be at a particular depth without having to go through a decompression stop. The tables also inform a diver how soon he can make a second or further dive. This is because there is nitrogen accumulation which must be dissipated.
An ordinary scuba diver finds it difficult to utilize the charts in his work. Devices that have been described which either mechanically or electrically store such information are to my knowledge, very elaborate, large and totally impractical.
There is a device marketed by Princton Techtronics of Hightstown, New Jersey entitled "Bottom Timer" which comprises a pressure-activated stop watch that sets the time in motion when an approximate depth of five to nine feet is obtained. The watch will continue to run recording the elapsed time until the activating depth is reached again. However, this device has to be manually reset before repetitive dive. Further the device gives no indication of the time spent on the surface or "surface interval time".
The variables required for correct interpretation of the United States Navy Dive Tables are maximum depth of dive, bottom time, repetitive diving group designation, surface interval time and residual nitrogen time. The Princton Techtronics device only measures bottom time and thus leaves open the danger of improper utilization of the tables.
Prior art which has been considered in the preparation of this patent application comprise the following United States and foreign patents: U.S. Pat. No. 3,111,003 A. Droz Nov. 19, 1963; U.S. Pat. No. 3,377,860 F. J. Masters Apr. 16, 1968; U.S. Pat. No. 3,475,902 P. Wessel Nov. 4, 1969; U.S. Pat. No. 3,505,808 U. A. Eschle Apr. 14, 1970; U.S. Pat. No. 3,696,610 Charbonnier Oct. 10, 1972; U.S. Pat. No. 3,759,101 Borom et al. Sept. 18, 1973; U.S. Pat. No. 3,910,117 Wicklund Oct. 7, 1975; U.S. Pat. No. 3,992,949 Edmondson Nov. 23, 1976; U.S. Pat. No. 4,054,783 Seireg et al. Oct. 18, 1977; Swiss Pat. No. 365,027 1962 German Pat. No. 1,236,418 1962.
The prior art has been concerned with the problems of a diver and described devices which are of some assistance. However, none of the prior art references provides automatic monitoring for the diver through successive dives to prevent the need for decompression. Thus U.S. Pat. No. 3,696,610 is primarily concerned with indicating the duration of decompression. U.S. Pat. No. 3,377,860 is a combination watch and depth gauge which does not record bottom time and ascent time for post-dive indication. U.S. Pat. No. 3,992,949 is a combination depth gauge, watch and rate of ascent computer which does not provide any direct reading of bottom time or maximum depth.
One object of the present invention is to provide a compact inexpensive light weight device which can be worn by the diver and which can automatically provide him continuously with the necessary guidance so as to avoid the necessity of decompression during the series of successive dives.
Other objects and advantages of this invention will be apparent from the description and claims which follow taken together with the appended drawings.